Minority stressors adversely affect sexual minority persons. Although minority stress research has significantly contributed to evolving understandings of how social conditions influence well-being, this field of study has been largely concerned with stress as it is experienced by individuals. However, when sexual minority individuals form intimate partnerships, they begin to share additional stressors as a result of becoming part of a same-sex couple. For example, on their own, some gay or lesbian individuals may not experience stigma, prejudice, or discrimination, but if they publicly declare themselves to be coupled, their sexual minority status is made visible in new ways, thereby increasing their odds of exposure to minority stressors. Therefore, we propose to examine minority stress as experienced by same-sex couples in order to understand the unique impact of couple-level minority stress on relationship quality and mental health. We will investigate how same- sex couples experience both eventful and chronic minority stressors as sexual minority persons (e.g., concealment of their gay/lesbian identity), as well as in their dyadic experiences within same-sex couples (e.g., concealment of their relationship). We propose a multi-method, three-phase research project that will take place over a five-year period. Our specific aims are to: Identify previously unexamined stressors that same-sex couples experience due to their sexual minority status (Specific Aim 1); Develop new scale measures of couple-level minority stressors and assess their psychometric properties (Specific Aim 2); and assess the relationships among couple-level minority stressors, relationship quality, and mental health as they evolve over time (Specific Aim 3). To achieve Specific Aim 3, we propose to examine data from a two-wave panel survey of a diverse sample of same-sex couples, with a 12-month time interval. We hypothesize that: Hypothesis 1: Increases in individual-level minority stressors are associated with negative mental health outcomes over a 12- month period (e.g., mood disorders, substance use/abuse), net the effects of sociodemographic and health- related controls (including Wave 1 mental health); Hypothesis 2: Increases in couple-level minority stressors are associated with negative mental health outcomes over a 12-month period, net the effects of individual-level minority stressors, and sociodemographic and health-related controls (including Wave 1 mental health); and Hypothesis 3: Changes in individual-level minority stressors, couple-level minority stressors, and relationship quality (e.g., relationship satisfaction and conflict) are interrelated in ways that demonstrate stress proliferation effects on mental health outcomes over a 12-month period, net the effects of sociodemographic and health- related controls (including Wave 1 mental health). The proposed work will extend existing stress theories, providing a foundation for future studies of stress proliferation in intimate relationships and mental health more generally. Further, by providing an understanding of how minority stress affects the well-being of same-sex couples, the study's findings will also inform future interventions and educational programs.